The assembly of the present invention has particular although not exclusive utility in supporting a dental control unit on which dental instruments, such as handpieces, syringes, and the like, as well as the usual controls for the instruments, are removably mounted, and the assembly enables the control unit to be conveniently positioned over the dental chair so that the instruments are readily accessible to the dentist in his direct working area; the control unit being movable vertically and horizontally by the dentist to a desired position. As mentioned above, the assembly of the invention may also be used for supporting other units in adjustable vertical and horizontal positions.
Accordingly, an important objective of the invention is to provide an improved spring counter-balanced arm assembly which is rugged in its construction, and which permits the supported unit to be set at any desired vertical level. The setting of the supported unit at any desired vertical level is achieved by the assembly, and the supported unit may be locked at any desired vertical level by an air operated lock. In addition, means is provided for leveling the supported unit in a horizontal plane after it has been set to the desired vertical level.